CN107899608B - Preparation method of self-supporting metal modified Beta molecular sieve and application of self-supporting metal modified Beta molecular sieve in synthesis of isoprene - Google Patents

Preparation method of self-supporting metal modified Beta molecular sieve and application of self-supporting metal modified Beta molecular sieve in synthesis of isoprene Download PDF

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CN107899608B
CN107899608B CN201711190821.6A CN201711190821A CN107899608B CN 107899608 B CN107899608 B CN 107899608B CN 201711190821 A CN201711190821 A CN 201711190821A CN 107899608 B CN107899608 B CN 107899608B
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molecular sieve
beta molecular
self
metal
catalyst
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CN107899608A (en
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白晨曦
曾尚景
刘士俊
代全权
崔龙
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Changchun Institute of Applied Chemistry of CAS
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J29/00—Catalysts comprising molecular sieves
    • B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
    • B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
    • B01J29/70—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of types characterised by their specific structure not provided for in groups B01J29/08 - B01J29/65
    • B01J29/7007—Zeolite Beta
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J29/00—Catalysts comprising molecular sieves
    • B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
    • B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
    • B01J29/70—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of types characterised by their specific structure not provided for in groups B01J29/08 - B01J29/65
    • B01J29/72—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of types characterised by their specific structure not provided for in groups B01J29/08 - B01J29/65 containing iron group metals, noble metals or copper
    • B01J29/76—Iron group metals or copper
    • B01J29/7615—Zeolite Beta
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C2/00—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms
    • C07C2/86—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms by condensation between a hydrocarbon and a non-hydrocarbon
    • C07C2/862—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms by condensation between a hydrocarbon and a non-hydrocarbon the non-hydrocarbon contains only oxygen as hetero-atoms
    • C07C2/867—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms by condensation between a hydrocarbon and a non-hydrocarbon the non-hydrocarbon contains only oxygen as hetero-atoms the non-hydrocarbon is an aldehyde or a ketone
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2229/00—Aspects of molecular sieve catalysts not covered by B01J29/00
    • B01J2229/10—After treatment, characterised by the effect to be obtained
    • B01J2229/18—After treatment, characterised by the effect to be obtained to introduce other elements into or onto the molecular sieve itself
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C2529/00—Catalysts comprising molecular sieves
    • C07C2529/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites, pillared clays
    • C07C2529/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
    • C07C2529/70—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of types characterised by their specific structure not provided for in groups C07C2529/08 - C07C2529/65
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C2529/00—Catalysts comprising molecular sieves
    • C07C2529/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites, pillared clays
    • C07C2529/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
    • C07C2529/70—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of types characterised by their specific structure not provided for in groups C07C2529/08 - C07C2529/65
    • C07C2529/72—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of types characterised by their specific structure not provided for in groups C07C2529/08 - C07C2529/65 containing iron group metals, noble metals or copper
    • C07C2529/76—Iron group metals or copper

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  • Catalysts (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

Abstract

The invention provides a preparation method of a self-supporting metal modified Beta molecular sieve, which comprises the following steps of firstly, dipping silica gel particles into a metal salt solution to obtain a precursor containing metal; and then mixing the metal-containing precursor obtained in the step with an alkaline template agent for forming the Beta molecular sieve, performing crystallization treatment, and roasting to obtain the self-supporting metal modified Beta molecular sieve. The invention directly compounds the active metal with silica gel, and then synthesizes and forms the molecular sieve, thereby realizing the one-step preparation of the self-supporting metal-Beta zeolite molecular sieve catalyst, being capable of preparing solid acid catalysts with different acid strengths, avoiding the complex procedure of the later forming of the catalyst.

Description

Preparation method of self-supporting metal modified Beta molecular sieve and application of self-supporting metal modified Beta molecular sieve in synthesis of isoprene
Technical Field
The invention relates to the technical field of solid catalyst synthesis, relates to a preparation method and application of a modified Beta molecular sieve, and particularly relates to a preparation method of a self-supporting metal modified Beta molecular sieve and application of the self-supporting metal modified Beta molecular sieve in isoprene synthesis.
Background
Isoprene is a colorless volatile organic chemical raw material, has a conjugated double bond structure, and is mainly used in the fields of synthetic rubber and fine chemical products. At present, the main preparation methods of isoprene are divided into physical separation methods and chemical synthesis methods. The physical separation method is the earliest method for producing isoprene, ethylene is prepared by cracking naphtha and then carbon five fractions are extracted, and the physical separation method for preparing isoprene is greatly restricted along with shortage of petroleum resources and new ethylene process development. The chemical synthesis method mainly comprises an isobutene-formaldehyde method, an acetylene acetone method and a propylene dimerization method, wherein the olefine aldehyde method has the advantages of simple process, small investment and relatively low raw material cost, and two-step industrialization is realized in the Soviet Union, Japan and the French successively. However, the two-step method of preparing isoprene from olefine aldehyde requires the use of a liquid acid catalyst, which has serious influence on the environment and ecology.
In recent years, solid acid catalysts used for the catalytic reaction have become a research hotspot because of the advantages of low energy consumption, small investment and the like in one-step catalysis of isobutene and formaldehyde to synthesize isoprene, the solid acid catalysts are important catalysts in acid-base catalysts, and the catalytic function is derived from an acid site with catalytic activity on the surface of a solid, namely an acid center, and most of the solid acid catalysts are oxides or mixed oxides of non-transition elements. However, these catalysts also have the problems of low reaction catalytic activity and complex catalyst preparation process, and specifically show the disadvantages of high catalyst preparation cost, long period, poor product selectivity, low raw material utilization rate and the like, and continuous improvement is still needed.
The solid acid catalyst used in the existing olefine aldehyde reaction mainly comprises phosphate, metal oxide and a molecular sieve, particularly a molecular sieve solid acid catalyst, and an inorganic microporous material with a regular pore channel structure. Especially Beta molecular sieve, high silicon zeolite with cross twelve circular ring channel system, acid catalysis characteristic and structure selectivity, and high heat stability, hydrothermal stability and wear resistance, so that it has excellent hydrothermal stability and coking resistance in a series of catalytic reactions.
However, the Beta molecular sieve has the problems of complex preparation process, long period and the like, in the general Beta molecular sieve synthesis method, most of the Beta molecular sieve synthesis methods are to mix silicon source, aluminum source, template agent and water to prepare sol slurry, crystallize for 3-60 days in a high-pressure kettle at 120-200 ℃ to obtain zeolite powder, modify the zeolite powder into functional zeolite powder by using metal or nonmetal at the later stage, and in the practical application of the catalytic process, the catalyst with certain granularity needs to be formed again, so the preparation process is complicated, the preparation cost of the catalyst is high, and the further popularization and application in the practical production are limited.
Therefore, how to find a more suitable Beta molecular sieve preparation process, which has a short period and a simple route and can reduce the production cost thereof, has become one of the focuses of great attention of many researchers in the industry.
Disclosure of Invention
In view of the above, the technical problem to be solved by the present invention is to provide a preparation method and an application of a modified Beta molecular sieve, and particularly to a preparation method of a self-supporting metal modified Beta molecular sieve and an application of the self-supporting metal modified Beta molecular sieve in isoprene synthesis.
The invention provides a preparation method of a self-supporting metal modified Beta molecular sieve, which comprises the following steps:
1) dipping the silica gel particles into a metal salt solution to obtain a precursor containing metal;
2) and (3) mixing the metal-containing precursor obtained in the step and an alkaline template agent for forming the Beta molecular sieve, crystallizing, and roasting to obtain the self-supporting metal modified Beta molecular sieve.
Preferably, the particle size of the silica gel particles is 0.05-0.7 mm;
the particle size of the self-supporting metal modified Beta molecular sieve is 0.05-0.7 mm.
Preferably, the metal salt comprises one or more of nitrate, sulfate, chloride and acetate of metal;
the metal in the metal salt is selected from one or more of iron, aluminum, nickel, copper, manganese, magnesium, zinc, cerium, silver and chromium.
Preferably, the metal salt further comprises a palladium compound and/or a platinum compound;
the mass concentration of the metal salt solution is 0.2-10%.
Preferably, the dipping time is 2-8 hours;
the step of drying is also included after the dipping;
the drying temperature is 80-150 ℃.
Preferably, the alkaline template for forming the Beta molecular sieve comprises one or more of tetraethylammonium hydroxide, tetraethylammonium bromide, tetraethylammonium chloride, tetraethylammonium iodide, hexadecyltrimethylammonium bromide, dimethylethylcyclohexylammonium hydroxide and trimethylcyclohexylammonium hydroxide;
the mass of the alkaline template agent for forming the Beta molecular sieve accounts for 10-80% of the mass of the silica gel particles.
Preferably, the alkaline template for forming the Beta molecular sieve is alkaline template solution for forming the Beta molecular sieve;
the mass concentration of the alkaline template solution for forming the Beta molecular sieve is 20-40%.
Preferably, the temperature of the crystallization treatment is 160-200 ℃;
the crystallization treatment time is 10-96 hours;
the roasting temperature is 500-600 ℃;
the roasting time is 5-8 hours.
The invention also provides application of the self-supporting metal modified Beta molecular sieve prepared by the preparation method in any one of the technical schemes in the field of catalysts.
Preferably, the catalyst comprises a catalyst for producing isoprene.
The invention provides a preparation method of a self-supporting metal modified Beta molecular sieve, which comprises the following steps of firstly, dipping silica gel particles into a metal salt solution to obtain a precursor containing metal; and then mixing the metal-containing precursor obtained in the step with an alkaline template agent for forming the Beta molecular sieve, performing crystallization treatment, and roasting to obtain the self-supporting metal modified Beta molecular sieve. Compared with the prior art, the invention aims at the defects of complex preparation process and long period of the existing Beta molecular sieve, and particularly aims at solving the problem that the Beta molecular sieve can be used for catalysis only by preparing zeolite powder by mixed sol crystallization, then modifying the zeolite powder and forming large particles in the later period.
According to the invention, modified metal is creatively directly compounded with silica gel, and then molecular sieve preparation and forming are directly carried out, so that the self-supporting metal-Beta zeolite molecular sieve catalyst is prepared in one step, solid acid catalysts with different acid strengths can be prepared, and complicated processes of late modification and forming of the catalyst are avoided. The invention uses the formed silica gel as a self-supporting carrier and a zeolite precursor, and obtains the self-supporting formed catalyst by one-step crystallization after adding metal salt, thereby avoiding the complex procedure of forming after traditional Beta powder and reducing the catalyst cost.
The preparation method provided by the invention has the advantages of mild and rapid conditions and simple process, reduces the discharge of industrial wastewater and waste gas, greatly reduces the preparation cost of the catalyst, and has better raw material conversion rate and product yield when the self-supporting metal modified Beta molecular sieve provided by the invention is used for catalyzing and synthesizing isoprene, thereby being beneficial to industrial production and popularization and application of the metal-Beta zeolite molecular sieve catalyst.
Experimental results show that the method provided by the invention greatly simplifies the steps of synthesizing and forming the catalyst, reduces the emission of industrial waste water and waste gas, greatly reduces the production cost, and in the process of catalyzing and continuously preparing the isoprene monomer, the conversion per pass of formaldehyde reaches more than 80%, and the yield of isoprene reaches more than 45%.
Drawings
FIG. 1 is an SEM image of a self-supporting metal modified Beta molecular sieve prepared in example 1 of the present invention;
FIG. 2 is an XRD diffractogram of the self-supported metal modified Beta molecular sieve prepared in example 1 of the present invention.
Detailed Description
For a further understanding of the invention, reference will now be made to the preferred embodiments of the invention by way of example, and it is to be understood that the description is intended to further illustrate features and advantages of the invention, and not to limit the scope of the claims.
All of the starting materials of the present invention, without particular limitation as to their source, may be purchased commercially or prepared according to conventional methods well known to those skilled in the art.
All the raw materials of the present invention are not particularly limited in their purity, and the present invention preferably employs purity requirements that are conventional in the art of analytical purification or molecular sieve catalyst preparation.
All the raw materials, the marks and the acronyms thereof belong to the conventional marks and acronyms in the field, each mark and acronym is clear and definite in the field of related application, and the raw materials can be purchased from the market or prepared by a conventional method by the technical staff in the field according to the marks, the acronyms and the corresponding application.
The invention provides a preparation method of a self-supporting metal modified Beta molecular sieve, which comprises the following steps:
1) dipping the silica gel particles into a metal salt solution to obtain a precursor containing metal;
2) and (3) mixing the metal-containing precursor obtained in the step and an alkaline template agent for forming the Beta molecular sieve, crystallizing, and roasting to obtain the self-supporting metal modified Beta molecular sieve.
Firstly, dipping silica gel particles into a metal salt solution to obtain a precursor containing metal.
The silica gel particles and the parameters thereof are not particularly limited in the present invention, and those used for preparing molecular sieves and the parameters thereof, which are well known to those skilled in the art, can be selected and adjusted according to the actual application, the product requirements and the quality requirements, and the silica gel particles are preferably dried silica gel particles. In order to facilitate the application of the catalytic process, the particle size of the silica gel particles is preferably 0.05-0.7 mm, more preferably 0.1-0.6 mm, more preferably 0.3-0.4 mm, and specifically can be
0.2～0.4mm。
The metal salt is not particularly limited in the present invention, and may be a metal salt used for modifying the molecular sieve, which is well known to those skilled in the art, and can be selected and adjusted by those skilled in the art according to the actual application, the product requirements and the quality requirements, and for the convenience of impregnation, the metal salt preferably includes one or more of nitrate, sulfate, chloride and acetate of the metal, more preferably nitrate, sulfate, chloride or acetate, and more preferably nitrate.
The selection of the specific metal in the metal salt is not particularly limited, and the active metal for modifying the molecular sieve, which is well known to those skilled in the art, may be selected and adjusted by those skilled in the art according to the actual application, the product requirements and the quality requirements, and for the convenience of subsequent use, the metal in the metal salt of the present invention is preferably selected from one or more of iron, aluminum, nickel, copper, manganese, magnesium, zinc, cerium, silver or chromium, more preferably iron, aluminum, nickel, copper, manganese, magnesium, zinc, cerium, silver or chromium, and still more preferably aluminum, iron, copper, nickel or cerium.
In the present invention, in order to ensure the comprehensiveness of the final product, the metal salt according to the present invention also preferably includes a palladium compound and/or a platinum compound in a broad sense, and more preferably a palladium compound or a platinum compound.
The metal salt solution is not particularly limited in the present invention, and the concentration of the conventional metal salt solution known to those skilled in the art may be used, and those skilled in the art may select and adjust the concentration according to the actual production situation, the product requirement and the quality requirement, and the present invention facilitates the impregnation and the uniform dispersion of the metal in the pore channels of the silica gel particles, and the mass concentration of the metal salt solution is preferably 0.2% to 10%, more preferably 1% to 8%, more preferably 3% to 7%, and more preferably 4% to 6%.
The time for the impregnation is not particularly limited, and may be conventional time for such reaction, which is well known to those skilled in the art, and may be selected and adjusted by those skilled in the art according to actual production conditions, product requirements and quality requirements, and the time for the impregnation is preferably 0.2 to 8 hours, more preferably 3 to 7 hours, and even more preferably 4 to 6 hours.
The impregnation temperature is not particularly limited, and a person skilled in the art can select and adjust the impregnation temperature according to actual production conditions, product requirements and quality requirements, the process conditions provided by the invention are mild, and the impregnation can be carried out at room temperature, namely the impregnation temperature is preferably 0-40 ℃, more preferably 5-35 ℃, more preferably 10-30 ℃, and more preferably 15-25 ℃.
The invention is a complete and preferred integral preparation method, ensures the performance of the final product, and preferably also comprises a drying step after the impregnation.
The specific parameters of the drying step are not particularly limited, and the parameters of conventional drying known to those skilled in the art can be used, and those skilled in the art can select and adjust the parameters according to the actual production condition, the product requirement and the quality requirement, and the drying time in the invention is preferably 4-12 hours, more preferably 6-10 hours, and more preferably 7-9 hours. The drying temperature is preferably 80-150 ℃, more preferably 90-140 ℃, more preferably 100-130 ℃, and more preferably 110-120 ℃.
The invention is a refined preparation scheme, is convenient to apply and implement, and the steps can be as follows:
and (3) impregnating inorganic metal salt with a certain concentration on the silica gel particle carrier after drying pretreatment, and drying at high temperature to form the silica gel particles containing the metal precursor.
Finally, the precursor containing the metal obtained in the step and an alkaline template agent for forming the Beta molecular sieve are mixed and then crystallized, and the self-supporting metal modified Beta molecular sieve is obtained after roasting.
The specific choice of the basic template for forming the Beta molecular sieve is not particularly limited by the present invention, and can be selected and adjusted according to the actual production situation, product requirements and quality requirements by those skilled in the art, and the basic template for forming the Beta molecular sieve preferably comprises one or more of tetraethyl ammonium hydroxide, tetraethyl ammonium bromide, tetraethyl ammonium chloride, tetraethyl ammonium iodide, hexadecyl trimethyl ammonium bromide, dimethyl ethyl cyclohexyl ammonium hydroxide and trimethyl cyclohexyl ammonium hydroxide, more preferably tetraethyl ammonium hydroxide, tetraethyl ammonium bromide, tetraethyl ammonium chloride, tetraethyl ammonium iodide, hexadecyl trimethyl ammonium bromide, dimethyl ethyl cyclohexyl ammonium hydroxide or trimethyl cyclohexyl ammonium hydroxide, more preferably tetraethylammonium hydroxide or tetraethylammonium bromide.
The amount of the basic template agent for forming the Beta molecular sieve is not particularly limited, and may be selected and adjusted by those skilled in the art according to actual production conditions, product requirements and quality requirements, and the amount of the basic template agent for forming the Beta molecular sieve is preferably 10% to 80%, more preferably 20% to 70%, more preferably 30% to 60%, and more preferably 40% to 50% of the mass of the silica gel particles.
In order to facilitate the template agent to better form a molecular sieve structure, the alkaline template agent for forming the Beta molecular sieve is alkaline template agent solution for forming the Beta molecular sieve. The concentration of the alkaline template solution is not particularly limited in the present invention, and may be the conventional concentration of the template solution known to those skilled in the art, and those skilled in the art can select and adjust the concentration according to the actual production situation, product requirement and quality requirement, and the mass concentration of the alkaline template solution for forming the Beta molecular sieve in the present invention is preferably 20% to 40%, more preferably 22% to 38%, and more preferably 25% to 35%.
The crystallization time is not particularly limited in the present invention, and may be selected and adjusted by a person skilled in the art according to actual production conditions, product requirements and quality requirements, and is preferably 10 to 96 hours, more preferably 20 to 86 hours, more preferably 30 to 76 hours, and more preferably 40 to 66 hours.
The temperature of the crystallization treatment is not particularly limited in the present invention, and may be selected and adjusted according to the actual production situation, the product requirement and the quality requirement by those skilled in the art, and the temperature of the crystallization treatment in the present invention is preferably 160 to 200 ℃, more preferably 165 to 195 ℃, more preferably 170 to 190 ℃, more preferably 175 to 185 ℃, and most preferably 180 ℃.
The roasting time is not particularly limited, and the roasting time of the molecular sieve known to those skilled in the art can be selected and adjusted by those skilled in the art according to actual production conditions, product requirements and quality requirements, and is preferably 5 to 8 hours, more preferably 5.5 to 7.5 hours, and even more preferably 6 to 7 hours.
The calcination temperature is not particularly limited in the present invention, and the calcination temperature of the molecular sieve known to those skilled in the art may be used, and those skilled in the art may select and adjust the calcination temperature according to the actual production situation, the product requirement and the quality requirement, and the calcination temperature in the present invention is preferably 500 to 600 ℃, more preferably 510 to 590 ℃, more preferably 520 to 580 ℃, more preferably 540 to 560 ℃, and most preferably 550 ℃.
The invention is a refined preparation scheme, is convenient to apply and implement, and the steps can be as follows:
and (2) uniformly mixing the dried precursor silica gel obtained in the step with an organic alkaline template solution to obtain mixed wet silica gel, then placing the wet silica gel into a stainless steel reaction kettle, crystallizing for 36-60 hours at the temperature of 160-190 ℃, cooling, washing with water, and roasting in a high-temperature muffle furnace to finally obtain the metal modified Beta zeolite molecular sieve formed in one step.
The invention has no particular limitation on the particle size of the self-supporting metal modified Beta molecular sieve, and the self-supporting metal modified Beta molecular sieve with the particle size equivalent to that of the silica gel carrier can be directly obtained, wherein the particle size is preferably 0.05-0.7 mm, more preferably 0.1-0.6 mm, more preferably 0.3-0.4 mm, and particularly can be 0.2-0.4 mm, so that the application of the catalyst is facilitated. The particle size of the above-mentioned supported metal modified Beta molecular sieve can be changed by other means by those skilled in the art, and the present invention is not limited to other specific means.
The invention also provides application of the self-supporting metal modified Beta molecular sieve prepared by the preparation method in any one of the technical schemes in the field of catalysts.
The specific application aspect of the catalyst is not particularly limited in the present invention, and may be selected and adjusted by those skilled in the art according to the practical application, product requirements and quality requirements, according to the common application fields of such molecular sieves known to those skilled in the art, and the catalyst of the present invention preferably includes a catalyst for preparing isoprene, and more preferably a catalyst for a fixed bed continuous process isoprene synthesis reaction.
The specific preparation process of isoprene in the present invention is not particularly limited, and may be a preparation method of isoprene well known to those skilled in the art, and those skilled in the art may select and adjust according to actual production conditions, product requirements and quality requirements, and for convenience of implementation and comparison, the specific preparation process of pentadiene is preferably the following steps:
isobutene and formaldehyde are used as starting raw materials, the prepared self-supporting metal modified Beta molecular sieve is used as a catalyst, and catalytic reaction is carried out through a continuous reactor under the conditions that the reaction temperature is 250-400 ℃ and the molar ratio of the isobutene to the formaldehyde is 5-7, so that an isoprene target product is obtained.
The reaction temperature is preferably 250 to 400 ℃, more preferably 280 to 380 ℃, more preferably 300 to 350 ℃, and particularly 300 to 330 ℃. In the invention, the molar ratio of the isobutene to the formaldehyde is preferably (5-7): 1, more preferably (5.5 to 6.5): 1, specifically, can be (5-6): 1. the air speed of the feeding of the formaldehyde is preferably 0.3-3 h-1More preferably 0.8 to 2.5 hours-1More preferably 1.3 to 2 hours-1. The sources of the above-mentioned isobutene of the present invention may also be methyl tert-butyl ether and tert-butanol. The source of the formaldehyde in the present invention may be paraformaldehyde or an aqueous trioxymethylene solution, and a 37% formaldehyde solution is more preferable. The continuous reactor according to the invention preferably comprises a fixed bed, a fluidized bed or a moving bed reactor.
The invention compounds the active metal with the silica gel directly, and then carries on the synthesis and the shaping of the molecular sieve directly, through controlling the concrete parameter and step of the process, thus has realized the one-step preparation of the self-supporting metal-Beta zeolite molecular sieve catalyst, and can prepare the solid acid catalyst of different acid strength, have avoided the tedious process of catalyst later modification, shaping, the technological method that the invention provides, because adopt and soak the active metal salt on the silica gel first, and then use the alkaline template to carry on the crystallization reaction to the precursor, have avoided metal salt and alkaline template to mix directly and produce the precipitate effectively, and then can't obtain the inherent defect and technological prejudice of the self-supporting metal modified Beta zeolite further. The invention uses the formed silica gel as a self-supporting carrier and a zeolite precursor, and obtains the self-supporting formed catalyst by one-step crystallization after adding metal salt, thereby avoiding the complex procedure of forming after traditional Beta powder and reducing the catalyst cost.
The preparation method provided by the invention has the advantages of mild and rapid conditions and simple process, reduces the discharge of industrial wastewater and waste gas, greatly reduces the preparation cost of the catalyst, has better raw material conversion rate and product yield when being used for the catalytic synthesis of isoprene, and is beneficial to industrial production and popularization and application of the metal-Beta zeolite molecular sieve catalyst.
Experimental results show that the method provided by the invention greatly simplifies the steps of synthesizing and forming the catalyst, reduces the emission of industrial waste water and waste gas, greatly reduces the production cost, and in the process of catalyzing and continuously preparing the isoprene monomer, the conversion per pass of formaldehyde reaches more than 80%, and the yield of isoprene reaches more than 45%.
For further illustration of the present invention, the following examples are provided to describe the preparation and application of a modified Beta molecular sieve, but it should be understood that these examples are carried out on the premise of the technical solution of the present invention, and the detailed embodiments and specific procedures are given, only for further illustration of the features and advantages of the present invention, not for limitation of the claims of the present invention, and the scope of protection of the present invention is not limited to the following examples.
Example 1
0.63g of aluminum nitrate nonahydrate and 0.34g of zirconium nitrate are dissolved in 12ml of water, the solution is soaked on 10g of 40-80 mesh silica gel carrier, after the solution is soaked for two hours at room temperature, the silica gel is dried in an oven at 110 ℃ for 12 hours, the dried aluminum-zirconium-loaded silica gel and 10ml of tetraethylammonium hydroxide (35%) are mixed and then put into a reaction kettle, the crystallization is carried out at 180 ℃ for 36-58 hours, the drying and the roasting are carried out at 550 ℃ for 5 hours, and then the self-supported Zr-Beta catalyst is obtained.
The self-supporting metal modified Beta molecular sieve prepared in the embodiment 1 of the invention is characterized.
Referring to fig. 1, fig. 1 is an SEM image of a self-supporting metal modified Beta molecular sieve prepared in example 1 of the present invention.
As can be seen from FIG. 1, the modified Beta molecular sieve catalyst maintains the morphology and particle size of the original silica gel.
Referring to fig. 2, fig. 2 is an XRD diffractogram of the self-supported metal modified Beta molecular sieve prepared in example 1 of the present invention.
As can be seen from FIG. 2, the catalyst is in the Beta crystal configuration.
The performance of the self-supporting metal modified Beta molecular sieve prepared in the embodiment 1 of the invention is detected.
The evaluation research of synthesizing isoprene by isobutene-formaldehyde one-step method is carried out on the catalyst by a fixed bed reactor:
under the action of 1g of the self-supported metal modified Beta molecular sieve catalyst prepared above and under normal pressure conditions, isobutylene and a formaldehyde solution with a mass concentration of 37% (molar ratio ═ 5.5:1) were co-fed and contacted with the catalyst, and the catalyst was reacted at 310 ℃ for 1 hour, followed by qualitative analysis by GC-MS and quantitative analysis by gas chromatography.
Formaldehyde conversion rate (amount of formaldehyde converted/total amount of formaldehyde) × 100%
Isoprene yield (amount of isoprene produced/total amount of formaldehyde) × 100
The results showed that the formaldehyde conversion was 88.6% and the isoprene yield was 47.8%.
Example 2
The other conditions for carrying out the operation and the examination were the same as in example 1 except that the amount of zirconium nitrate added was changed to 0.17 g.
The prepared shaped catalyst is used in the reaction of preparing isoprene by the gas phase condensation of formaldehyde and isobutene.
The performance test of the self-supporting metal modified Beta molecular sieve prepared in the embodiment 2 of the invention shows that the formaldehyde conversion rate is 87.2% and the isoprene yield is 46.9%.
Example 3
0.63g of aluminum nitrate is dissolved in 12ml of water, the solution is soaked on 10g of 40-80 mesh silica gel carrier, after the solution is soaked for two hours at room temperature, the dried sample is dried for 12 hours in a drying oven at 110 ℃, the dried sample is taken out and mixed with 10ml of tetraethylammonium hydroxide (35 percent), the mixture is put into a reaction kettle and crystallized for 48 hours at 180 ℃, and the self-supporting Beta catalyst is obtained after the mixture is dried and roasted for 5 hours at 550 ℃.
The prepared shaped catalyst is used in the reaction of preparing isoprene by the gas phase condensation of formaldehyde and isobutene.
The performance test of the self-supporting Beta molecular sieve prepared in the embodiment 3 of the invention shows that the formaldehyde conversion rate is 81.0% and the isoprene yield is 45.1%.
Example 4
Dissolving 0.34g of zirconium nitrate, 0.48g of copper nitrate and 0.05g of aluminum nitrate in 12ml of water, soaking the solution on 10g of 40-80-mesh silica gel carrier for two hours at room temperature, drying in an oven at 110 ℃ for 12 hours, taking out a dried sample, mixing with 10ml of tetraethylammonium hydroxide (35%), putting into a reaction kettle, crystallizing at 180 ℃ for 48 hours, drying, and roasting at 550 ℃ for 5 hours to obtain the self-supported ZrCu-Beta catalyst.
The prepared shaped catalyst is used in the reaction of preparing isoprene by the gas phase condensation of formaldehyde and isobutene.
The performance test of the self-supporting ZrCu-Beta molecular sieve prepared in the embodiment 4 of the invention shows that the formaldehyde conversion rate is 82.4%, and the isoprene yield is 49.0%.
Example 5
0.12g of ferric nitrate and 0.63g of aluminum nitrate are dissolved in 12ml of water, the solution is soaked on 10g of 40-80 mesh silica gel carrier, after the solution is soaked for two hours at room temperature, the dried sample is taken out and mixed with 10ml of tetraethylammonium hydroxide (35 percent) and then put into a reaction kettle, the mixture is crystallized for 48 hours at 180 ℃, and the crystallized product is dried and roasted for 5 hours at 550 ℃, thus obtaining the self-supporting Fe-Beta catalyst.
The prepared shaped catalyst is used in the reaction of preparing isoprene by the gas phase condensation of formaldehyde and isobutene.
The performance test of the self-supporting Fe-Beta molecular sieve prepared in the embodiment 5 of the invention shows that the formaldehyde conversion rate is 93.9% and the isoprene yield is 46.2%.
Example 6
0.16g of zirconium nitrate, 0.19g of nickel nitrate and 0.63g of aluminum nitrate are dissolved in 12ml of water, the solution is soaked on 10g of 40-80 mesh silica gel carrier, after soaking for two hours at room temperature, the silica gel carrier is dried in a 110 ℃ oven for 12 hours, a dried sample is taken out and mixed with 10ml of tetraethylammonium hydroxide (35 percent), the mixture is put into a reaction kettle and crystallized for 24-48 hours at 180 ℃, and the ZrNi-Beta catalyst is obtained after drying and roasting for 5 hours at 550 ℃.
The prepared shaped catalyst is used in the reaction of preparing isoprene by the gas phase condensation of formaldehyde and isobutene.
The performance test of the self-supporting ZrNi-Beta molecular sieve prepared in the embodiment 6 of the invention shows that the formaldehyde conversion rate is 91.1%, and the isoprene yield is 45.7%.
Comparative example 1
Dissolving 1.44g of sodium metaaluminate and 0.2g of sodium hydroxide in 10ml of tetraethylammonium hydroxide (35%), adding 25ml of deionized water, dropwise adding 5g of tetraethoxysilane into the solution, stirring for 4 hours, transferring the solution into a reaction kettle, crystallizing for 48 hours at the temperature of 180 ℃, cooling, washing and drying to obtain a powdery Beta molecular sieve sample, and roasting for 5 hours at the temperature of 550 ℃ to remove the organic template.
2g of the Beta molecular sieve raw powder prepared above is added into 100ml of ammonium nitrate solution (1 mol/L) and stirred for 4 hours in an oil bath at 80 ℃ to obtain the ammonium ion exchanged Beta molecular sieve, and after drying, the Beta molecular sieve raw powder is roasted for 5 hours at 550 ℃ to obtain an H-Beta molecular sieve powder sample.
0.12g of ferric nitrate was dissolved in 50ml of water, 2g of the H-Beta molecular sieve powder prepared above was added to the ferric nitrate solution, stirred in an oil bath at 80 ℃ for 2 hours, dried, and then calcined at 550 ℃ for 2 hours to obtain a sample of Fe-modified Beta molecular sieve powder.
Tabletting the modified Beta powder sample through a tablet machine, crushing, and separating catalyst particles of 40-80 meshes through a stainless steel metal mesh screen for later use.
The prepared shaped catalyst is used in the reaction of preparing isoprene by the gas phase condensation of formaldehyde and isobutene.
The performance test of the Fe-Beta molecular sieve prepared in comparative example 1 of the invention shows that the formaldehyde conversion rate is 80.5% and the isoprene yield is 40.3%.
According to the conventional process and results for preparing the Fe-Beta molecular sieve in the comparative example 1, the preparation process provided by the invention greatly simplifies the steps of synthesizing and forming the catalyst, reduces the discharge of industrial wastewater and waste gas, greatly reduces the production cost, and simultaneously has better raw material conversion rate and product yield.
The foregoing detailed description of the method for preparing a self-supporting metal-modified Beta molecular sieve and its use in the synthesis of isoprene provided by the present invention has been presented using specific examples to illustrate the principles and embodiments of the present invention, and the above examples are provided only to aid in the understanding of the methods and their core concepts, including the best mode, and to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any combination of the methods. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention. The scope of the invention is defined by the claims and may include other embodiments that occur to those skilled in the art. Such other embodiments are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.

Claims (8)

1. A preparation method of a catalyst for preparing isoprene is characterized by comprising the following steps:
1) dipping the silica gel particles into a metal salt solution to obtain a precursor containing metal;
2) mixing the metal-containing precursor obtained in the step with an alkaline template agent for forming the Beta molecular sieve, performing crystallization treatment, and roasting to obtain the self-supporting metal modified Beta molecular sieve;
the self-supporting metal modified Beta molecular sieve is a catalyst for preparing isoprene.
2. The method according to claim 1, wherein the silica gel particles have a particle size of 0.05 to 0.7 mm;
the particle size of the self-supporting metal modified Beta molecular sieve is 0.05-0.7 mm.
3. The preparation method of claim 1, wherein the metal salt comprises one or more of nitrate, sulfate, chloride and acetate of metal;
the metal in the metal salt is selected from one or more of iron, aluminum, nickel, copper, manganese, magnesium, zinc, cerium, silver and chromium.
4. The method according to claim 3, wherein the metal salt further comprises a palladium compound and/or a platinum compound;
the mass concentration of the metal salt solution is 0.2-10%.
5. The method according to claim 1, wherein the time for the immersion is 2 to 8 hours;
the step of drying is also included after the dipping;
the drying temperature is 80-150 ℃.
6. The preparation method according to claim 1, wherein the alkaline template for forming the Beta molecular sieve comprises one or more of tetraethylammonium hydroxide, tetraethylammonium bromide, tetraethylammonium chloride, tetraethylammonium iodide, hexadecyltrimethylammonium bromide, dimethylethylcyclohexylammonium hydroxide and trimethylcyclohexylammonium hydroxide;
the mass of the alkaline template agent for forming the Beta molecular sieve accounts for 10-80% of the mass of the silica gel particles.
7. The method according to claim 6, wherein the basic template for forming the Beta molecular sieve is a basic template solution for forming the Beta molecular sieve;
the mass concentration of the alkaline template solution for forming the Beta molecular sieve is 20-40%.
8. The method according to any one of claims 1 to 7, wherein the temperature of the crystallization treatment is 160 to 200 ℃;
the crystallization treatment time is 10-96 hours;
the roasting temperature is 500-600 ℃;
the roasting time is 5-8 hours.
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